years and years ago I read a superb book on aircraft carriers, their aircraft, their history and their operations. It was made in the early 1990ies, way before the F-18 assumed the tanker, electronic warfare and troop transport roles, and therefore it depicted a wonderful variety of carrier aircraft (Hawkeye, Viking, Prowler/Intruder, Tomcat, Harrier...).

The book said that all aircraft carriers are not armored due to an international treaty, so they are less resistant to e.g. torpedoes; and that Japan in World War II built battleships that "accidentally" received an aircraft deck, thus building aircraft carriers that were effectively armored.

Do I remember right? If so, what was the reason behind prohibiting aircraft carriers to be armored?

What we know from WWII is that the UK had armoured deck carriers and suffered less damage than the US Navy whose decks were unarmoured.
The treaties in force prior to WWII were probably all scrapped by the war, I'm inclined to believe if any current carrier US or otherwise is unarmoured its because of cost and weight.
The historians will chime in I'm sure.

Also when you are talking about torpedoes, there is a big difference between a WW2 torpedo and a modern one. The WW2 one hit the side of the ship (hence the creation of torpedo "blisters") and modern one that explodes under the ship creating an air bubble that breaks the keel of the ship.

Also armored is "relative". Do you mean a armored ship like a BB? Or do you mean that certain parts are protected? Todays carriers are not "armored" per say, but I'm sure parts are. I'm sure the hull is as thin as they can get away with, knowing that it is designed for 50 years of service, so about 2 inches thick. But I'm sure the "special weapons" mags are much thicker ( I know, no more of those onboard, so they tell us).

The thickest armor I aver seen was aboard a decommed Albany class CG. She had a 4 inch main deck. But the Iowa class had 20 inches of hardened steel in places(boggles the mind if you think about it, my ship had a 1/2 inch steel hull).

Quoting par13del (Reply 1):What we know from WWII is that the UK had armoured deck carriers and suffered less damage than the US Navy whose decks were unarmoured.

The US had wooden decks. Different trains of thought. Wooden was easier to repair, lighter weight. The steel(armored) was tougher, but cost topside weight, harder to repair. We learned that wood doesn't stop an armor piercing bomb but steel might. But since we had less "top weight" our hangars could be bigger and we could carry more aircraft. A trade off. Like I said, different trains of thought. We learned a lot from the Brits, shame that they couldn't afford to keep building carriers after the 60's. To think, the British thinking and the US pocketbook, what we could have made. A Brit/US SST, WOW, would still be flying. I regress, forgive me.

Quoting par13del (Reply 1):What we know from WWII is that the UK had armoured deck carriers and suffered less damage than the US Navy whose decks were unarmoured.

Thank you, but I knew that difference between British and U.S. carriers.

Quoting sprout5199 (Reply 2):Also armored is "relative". Do you mean a armored ship like a BB? Or do you mean that certain parts are protected?

I have to specifiy that I meant by "armored" that the hull below the waterline was armored - thus clearly pointing to the older torpedoes that detonated upon impact with the ship.

Having an above-waterline armor like a battleship makes not much sense, given that the aircraft on the deck would be destroyed anyway if it meets gunshells, bombs or kamikaze attacks.

So, if there was a real prohibition on amored aircraft carriers, USS Midway couldn't have been built?

On the Washington Naval Treaty wiki page, it says:

"Aircraft carriers were limited to 27,000 tons and could carry no more than 10 heavy guns, of a maximum calibre of 8 inches. However, each signatory was allowed to use two existing capital ship hulls for aircraft carriers, with a displacement limit of 33,000 tons each. (Articles IX and X)"

This is the only, albeit weak reference I could find that is pointing to a prohibition of armored aircraft carriers...

Thank you – perhaps I can dig a bit deeper and try to locate that book I mentioned in the first post.

Quoting sprout5199 (Reply 2):Also when you are talking about torpedoes, there is a big difference between a WW2 torpedo and a modern one. The WW2 one hit the side of the ship (hence the creation of torpedo "blisters") and modern one that explodes under the ship creating an air bubble that breaks the keel of the ship.

Torpedoes that did that were actually developed by all three major submarine forces *before* the war, but at the onset of the war, the Japanese had not fielded theirs (deciding to go for simpler contact hits and bigger warheads on bigger torpedoes*), and neither the German or American magnetic exploders (triggers) worked very well.

In both the German and American cases the fixes required to make the magnetic triggers effective were not that huge, but in both cases extreme secrecy and limited time and testing budgets (the latter was especially a problem for the USN), resulted in mechanisms that were not reliable, mainly because neither side really took into account the actual variability of the earth's magnetic field (so the original magnetic exploders for both sides worked well in the one spot on the planet each side conducted testing).

As an interesting aside, both the German and American torpedoes suffered three parallel problems at the beginning of the war - unreliable magnetic exploders as mentioned above, depth keeping problems (in both cases, consideration was not given to the gradual build up of pressure inside the submarine during extended periods submerged, which caused the reference pressure used for depth keeping in the torpedo to be high), and unreliable contact exploders (although the failures modes were completely different). The Germans, while initially discounting the problem reports from their submarines commanders (like the Americans did later), accepted and fixed their problem much more quickly than the Americans did.

*And the Long Lances were by far the best torpedoes in the first few years of the war, with excellent range, speed and reliability backed up with a large (and deadly) warhead. An unusually small wake (for a chemically power torpedo) was a nice advantage too.

The carriers the UK built prior to WW2, at least the dedicated ones rather than conversions, had deck armour due to the belief that the most likely area they might see action was the Mediterranean. Where they were expected to be in range of land based enemy aircraft.
The downside was a smaller complement of aircraft.

Quoting sprout5199 (Reply 2):The thickest armor I aver seen was aboard a decommed Albany class CG. She had a 4 inch main deck. But the Iowa class had 20 inches of hardened steel in places(boggles the mind if you think about it, my ship had a 1/2 inch steel hull).

Want to see a thick armored deck? Visit the museum BBs USS Massachusetts, USS Alabama (both are South Dakota, or SoDak class BBs), or any of the 4 Iowa class BBs. The two SoDaks, have hatches open through the nearly 6" armored deck you can pass through going up or down the latter to decks below. The weather decks were designed to initiate the fuze of AP shells, and the armored deck (often called the main deck or second deck) contained the exploding shell. Both the weather deck and main deck had splinter protection, too.

Quoting flyingturtle (Reply 4):I have to specifiy that I meant by "armored" that the hull below the waterline was armored - thus clearly pointing to the older torpedoes that detonated upon impact with the ship.

Having an above-waterline armor like a battleship makes not much sense, given that the aircraft on the deck would be destroyed anyway if it meets gunshells, bombs or kamikaze attacks.

For BBs, the belt armor was not normally part of the TDS (torpedo defense system), the belt was meant to reject AP shells of large BB caliber (14", 15", 16", and in some casese bigger shells). The armored belt extended (on most BBs) from above the waterline almost to the bottom of the ship's side, and were often tapered with the thickest portion at the top of the belt and the thinnest portion at the bottom. It was thought AP shells that hit the water short of the side of the BB would begin to loose energy as it traveled further through the water to hit the ship below the waterline, thus thinner armor plate was placed there.

The SoDak class had an armored belt as thick as 12.2" at the topp, thinning to 1" at the bottom and inclined at 19 degrees (thus the travel of the shell at most oblique angles would actually have to travel through more armor plate as it continued at its downward angle). I have been on the lower decks aboard the Massachusetts, and you can actually see the armor plate interior.

BBs and CVs used bulges and several compartments below the waterline to defeat torpedos, usually 4 or more compartments, some were empty and some were liquid filled (fuel or water). The SoDaks also incorproated an unusual skeg design for the outboard shafts that added extra torpedo protection to turrent #3 magazine. The skegs were part of the TDS.

USN CVNs of today have some armor protection below the waterline, and the hull is lined with kevlar for additional protection. These ships also have very strong longititual and lateral beams between the the inner and outer lower hulls of the double (or triple) bottoms that add strenght designed to defeat a torpedo exploding beneath the ship and creating the deadly bubble such as a Mk.48 torpedo creates.

Quoting flyingturtle (Thread starter):Do I remember right? If so, what was the reason behind prohibiting aircraft carriers to be armored?

I think this thread has answered the question for you, but the bottom line is that many carriers built to the Washington Treaty standard DID have armor. The amount they could use was limited by the competing desire to construct a very large ship on a limited displacement.

Quoting KC135TopBoom (Reply 10):Want to see a thick armored deck? Visit the museum BBs USS Massachusetts, USS Alabama (both are South Dakota, or SoDak class BBs), or any of the 4 Iowa class BBs.

Despite living in Alabama for years I've never been to see the USS Alabama. Some day I'm definitely going to tour it. I enjoyed getting to see the USS Intrepid last year in New York--I just wish we could've seen more of the ship.

Quoting KC135TopBoom (Reply 10):Want to see a thick armored deck? Visit the museum BBs USS Massachusetts, USS Alabama (both are South Dakota, or SoDak class BBs), or any of the 4 Iowa class BBs.

I have visited the Wisconsin in Norfolk Virginia , is impressive. I knocked on the armored citadel, thinking it would sound like knocking on a steel plate. NOPE no sound at all. FREAKING IMPRESSIVE.

Quoting MD-90 (Reply 13):Despite living in Alabama for years I've never been to see the USS Alabama.

GO SEEIT. I was in Norfolk for a class and went on the WORST day ever, Mid 40's drizzle, but my buddy and I spent 5 hours just walking around the main deck. couldn't go below, what a shame, was still in "ready reserve" status. WAS GREAT. The best thing seeing the Albany class CG was we went to it to get parts for my ship(it was decommed awaiting disposal). So we had the run of the ship. Talos missiles are bad ass, was an awesome ship. There was two rubber belts that circled the ship 1/3 and 2/3rds the length, to prevent "hogging" and the bridge was like 100 feet above the water line, must have been fun in high seas.

Quoting sprout5199 (Reply 14):I have visited the Wisconsin in Norfolk Virginia , is impressive. I knocked on the armored citadel, thinking it would sound like knocking on a steel plate. NOPE no sound at all. FREAKING IMPRESSIVE.

Quoting SmittyOne (Reply 11):I think this thread has answered the question for you, but the bottom line is that many carriers built to the Washington Treaty standard DID have armor. The amount they could use was limited by the competing desire to construct a very large ship on a limited displacement.

The Washington Naval Treaty limited aircraft carrier size to 27,000 tons, however each signatory was allowed to convert 2 existing ships to aircraft carriers with a maximum displacement of 33,000 tons. Furthermore, maximum tonnage for each signatory nation was restricted; the USN and Royal Navy were allowed up to 135,000 tons, the Japanese were restricted to 81,000 tons, and the French and Italians could have 60,000 tons each.

The Second London Naval Treaty, further limited carrier size to an upper limit of 23,000 tons. However, the various naval treaties were effectively ignored towards the later 1930's, and a large build up of carriers started again.

The thing about treaties like this is those that are in the "top end" comply, and those that aren't, don't and you get a false sense of security for those in the "top end" and a rejection of all treaties after from all others. Thats one reason why I dont like the non-proliferation treaties about nukes. Once a country shows(tests) that they have a bomb even if they are not part of the "gang" they soon will be part of that "gang". I digress again(beers will do that).

I think that armor went the way of the big gun, nice to have but are we going to use it? Until a ship is hit and we didn't learn from the past,we are doomed to repeat it. Does a carrier need enough to stop a 16 inch shell?NO but how about enough to stop an RPG? I'm sure a well placed RPG hit into the side of a CVN would cause a lot of damage. IIRC when the Stark was hit one missile actually went completely through the ship. As far as torps are concerned, not sure armor can do anything. Maybe a anti-torpedo torpedo, have thought about that one. Why not? Sonar can tell when a torp is inbound, launch a small torp to hit the inbound with about 10 pounds of H.E. Makes sense to me, use a missile to hit a missile, use a torp to hit a torp. God let me design the next small ship, would be under budget, under time, and BAD ASS. Ya Right, mine would launch the space shuttle for a side job. Beer talking again.

Does Armor matter anymore? I thought that current torpedoes actually detonated under the keel to break the boat instead of actually impacting for damage. I hope I did not miss that point in prior postings.

Quoting sprout5199 (Reply 17):Maybe a anti-torpedo torpedo, have thought about that one. Why not? Sonar can tell when a torp is inbound, launch a small torp to hit the inbound with about 10 pounds of H.E. Makes sense to me, use a missile to hit a missile, use a torp to hit a torp.

Dan this is not nearly as dumb as it sounds - I can't believe that (as far as we know) no one has developed it yet.

Quoting beau222 (Reply 18):Does Armor matter anymore? I thought that current torpedoes actually detonated under the keel to break the boat instead of actually impacting for damage. I hope I did not miss that point in prior postings.

Against torpedoes, armor is pretty useless...however, some armor protection for magazines and other critical spaces can protect them from indirect impacts of missles/torpedoes and prevent a catastrophic loss.

One thing a lot of people probably don't realize is that armor protection has historically been RELATIVELY INEFFECTIVE in naval combat. Armor systems intended to counter shellfire must be designed with a 'zone of immunity' in mind...a safe spot in between the closest range at which the side armor can defeat a flat shot and the longest range at which the deck armor can defeat a plunging shot.

Unfortunately, at the close ranges where a lot of World War 2 gun battles took place (especially in the Pacific) main caliber rounds tore their targets to shreds. Likewise, the lack of ability to validate 'side protection systems' in real-world conditions resulted in a lot of capital ships taking much worse damage from torpedo hits than anticipated.

In 2012, a ship's survivability and combat power depend on a steady flow of electrical power / integrity of electronic networks, radar arrays etc. - fairly sensitive stuff so the key is to prevent hits in the first place.

Quoting SmittyOne (Reply 19):Quoting sprout5199 (Reply 17):
Maybe a anti-torpedo torpedo, have thought about that one. Why not? Sonar can tell when a torp is inbound, launch a small torp to hit the inbound with about 10 pounds of H.E. Makes sense to me, use a missile to hit a missile, use a torp to hit a torp.

Dan this is not nearly as dumb as it sounds - I can't believe that (as far as we know) no one has developed it yet.

Quoting MD-90 (Reply 13):Despite living in Alabama for years I've never been to see the USS Alabama. Some day I'm definitely going to tour it. I enjoyed getting to see the USS Intrepid last year in New York--I just wish we could've seen more of the ship

You should go. I live in Daytona Beach but have been there once back in the 90's. The USS Alabama and USS Drum were very interesting, but as an aviation guy it was seeing an A-12 Blackbird that made the trip for me.

The USS Missouri in Pearl Harbor is worth a visit too. The thickness of the armor around the battle helm station really amazed me. From the aviation standpoint, what really made an impression on me was standing on the bridge and looking across the harbor. Only then did I realize how narrow it is and how difficult it must have been for the attacking Japanese Nakajima B5N Vals to launch torpedoes at Battleship Row.

Most US Navy, JMSDF ships I've been upon have some 'armor' around the magazines. While protecting against penetration of the magazine is important, it is also to protect the rest of the ship from a 'minor' explosion in the magazine. That includes aircraft carriers.

Quoting flyingturtle (Reply 4):I could find that is pointing to a prohibition of armored aircraft carriers...

According to Wikipedia

CV-4 - the USS Ranger - laid down in Sept 1931 - commissioned in 1934 had 2 inch 'armor' at the belt and bulkheads, with 1 inch deck over the steering gear. She was the US first 'keel up' carrier. As mentioned above - 2 inch is about as thin of steel as you could probably use to build a carrier.

CV-5 - the USS Yorktown - laid down in May 1934 - commissioned 30 Sep 1937 - had 2.5 inch to 4 inch belt armor, 4 inch bulkheads, 4 inch sides and 4 inches over the steering gear. She was clearly built with armor protection as a standard criteria.

CVE-63 - the USS Midway - laid down in Jan 1943 - commissioned 23 Oct 1943 - did not have any armor listed. Kaiser built those ships fast and light. She fought in the Pacific until October 1944 when the ship name was changed to USS St Lo.

CV-41 - the last USS Midway - laid down Oct 1943 - commissioned 10 Sep 1945 - had some limited armor. By the time I was stationed in Yokosuka in 1982 - I don't think she had any special armor left. During her 1986 dry dock in Yokosuka - the added sea keeping blisters (I don't know if they were in addition or replacement of previous blisters).

You want to talk about BIG - I got to walk down on the dry dock floor under the turn of her bilge. Friend of mine was one of the SRF project managers - in charge of the new blisters.

Quoting flyingturtle (Reply 4):So, if there was a real prohibition on amored aircraft carriers, USS Midway couldn't have been built?

Both USS Midway carriers were designed and built long after the Washington Treaty limitations were no longer even considered.

As I note above - the USS Yorktown appears to be built in contravention of the treaty - and the 1940 designed USS Essex - CV-9 - clearly was not built to Washington Treaty standards.

The references I see say the Washington Treaty effectively ended at the end of 1936.

Quoting HaveBlue (Reply 22):You should go. I live in Daytona Beach but have been there once back in the 90's. The USS Alabama and USS Drum were very interesting, but as an aviation guy it was seeing an A-12 Blackbird that made the trip for me

Alabama has at least three A-12/SR-71s. I've seen the one at the Space & Rocket Center numerous times (which apparently is an A-12 since it's a single seater) and there's also one at the Southern Museum of Flight in Birmingham.

My dad's been on both and he said the USS Drum is extremely cramped--still, I'd bet it be interesting. I'll make sure to bring a wide angle lens when I go.

Quoting rfields5421 (Reply 24):As I note above - the USS Yorktown appears to be built in contravention of the treaty - and the 1940 designed USS Essex - CV-9 - clearly was not built to Washington Treaty standards.

The Washington Naval Treaty specified a maximum displacement a carrier could be at 27,000 tons with a total tonnage for USN of 135,000 tons. Yorktown was under that maximum restriction. It was not until the USN built USS Wasp that the USN hit the 135,000 ton limit, meaning the USN had 6 carriers under the Washington Naval Treaty (Langley, Lexington, Saratoga, Ranger, Yorktown, Enterprise and Wasp).

The Second London Naval Treaty removed the cap on number of warships, but limited new carrier builds to under 23,000 tons.

With the Washington Naval Treaty no longer in force after the mid 1930's and the collapse of the Second London Naval Treaty, the USN proceeded to build Hornet in the interim, and proceeded to refine the design free from arms limitations into the Essex class carriers.

The Royal Navy on the other hand had Eagle, Courageous, Glorious, Furious, Argus, Hermes, Ark Royal, as their Washington Naval Treaty carriers. Illustrious, Formidable, Victorious, and Indomitable followed as their Second London Naval Treaty restricted carriers.

The RN then added Unicorn as a aircraft repair ship and a light carrier. The RN then built the Implacable class, which were a slightly refined version of the Illustrious class carrier (new features included moving to 4 engined propulsion rather than 3, slimmer hangar walls, an additional lower hangar, and adopted a permanent deck park. During WWII, the RN planned for, but never built the Malta class carriers, which would have been essentially the RN's version of the USN Midway class carriers. They did complete 15 of the 1942 Design Light Fleet Carriers (the Colossus and the Majestic class carriers), of which many were sold overseas, 2 of the Audacious class carriers, and 4 of the Centaur class carriers.

It should be noted that the RN armored carriers had for the most part fairly short service lives after the war, some of which was due to the major damage that was accumulated over the years that was extremely costly to fix, and because RN build quality suffered during the war. Indefatigable and Implacable were built badly (as were most British wartime ships - Admiralty records related to planned reconstructions implicitly give war-built cruisers a life of only ten years). No criticism intended there - emphasis was on quantity rather than quality.

The box armor requirement dragged a crowd of design burdens on its coattails in terms of structure, lift configuration, freeboard, habitability, ship’s speed. But the salient fact, overshadowing all others, was the limit it imposed on air complement. Here, however, a fundamental misconception has clouded the armor debate; the RN's leadership’s decision for smaller air groups preceded the flight deck armor, a feature subsequently superimposed on the preliminary design work.

These two steps, though distinct, became inseparably meshed in the design’s wartime shortcomings and thus must be considered together. The small-group specification put the ships at an initial disadvantage, and the armor then canceled any hope for a remedy, cramping the hangars and reducing the space available for deck parks.

As the Washington Naval Treaty and the Second London treaty expiration date drew near, the British foresaw their freedom to build multiple carriers, which led them to think they need not crowd each individual ship with a powerful air complement - the dubious decision that made the armored carrier possible. It paralleled the navy’s willingness to build small but numerous cruisers, though along a different line of thought - design studies revealed that small carriers would prove cost-ineffective and operationally inferior; yet small air groups had an allure in keeping FAA size manageable for budgetary concerns while reducing risk to having large portions of the FAA lost if a carrier is sunk. While no one dared apply such logic to battleships—arguing for only two or three guns per ship - it had some validity as applied to carriers in view of the limited FAA resources at the time. However, it forfeited the potential impetus for increased procurement inherent in a fleet of half-empty carriers, and it neglected any consideration of wartime mobilization.

All the extra armor RN carriers had was to detonate higher in the hull, which certainly enhanced survivability, though not in the way the designers intended. The hangars and their planes suffered increased damage, but crippling damage to the vitals became less likely. There’s no debating the advantage of this; yet debate continues, and properly so, because of the extra ounce of prevention the ships could have enjoyed with a larger CAP.

Accepting a small fighter group meant accepting a greater probability of bomb hits, with the hopes of minimizing the damage those bombs caused - which is completely backwards thinking but it made sense to someone at the time. Of course, the carrier’s escorts might dispute the entire notion of minimizing the damage - the armored box did them no good, in contrast to the universal blessing of a hefty CAP. And hangar armor, unlike fighters, could never counter a flight of torpedo planes.

Apart from this self-defense issue, a larger, American-sized air group would have greatly increased the ships’ offensive capability. With a larger airgroup, the British could have accomplished much more at Taranto, probably putting more of the Italian Navy out of commission longer. Vittorio Veneto and more of the Italian fleet probably would not have survived Matapan if attacked by twice as many Albacores.

Reminds me of an old line "Sufficient quantity can create quality on its own"

As much as I've studied WWII history, I always remember they didn't have anywhere near the information we have today to assist their decision making process. It is easy to look back and say they should have done this or that - and totally unfair.

While a number of great ships, aircraft and weapons were built for WWII, it was the shear weight of the quantity of the various weapons that the US was able to build that significantly helped overwhelm the Axis powers.

Quoting sprout5199 (Reply 15):NO but how about enough to stop an RPG? I'm sure a well placed RPG hit into the side of a CVN would cause a lot of damage. IIRC when the Stark was hit one missile actually went completely through the ship.

This is more than a bit looney. Hitting a CVN with an RPG on the side would be the like firing your pellet gun at an elephant. RPG's are designed to cut through armor with a shaped charge warhead and may get through the sidewalls of a carrier but they are not going to punch through multiple void spaces and compartments to get to anything even remotely critical.

US CVN's are designed with protection in mind. While they don't have traditional side or deck armor in the way one might know it from the WWII era this is more because of the change in threat than anything. The focus was not on rejecting shells/bombs but on limiting damage from missiles and torpedoes. This is done by sub-division, some armor plating and some kevlar protection around critical spaces.

It is highly classified enough that there is one recorded sink-ex ever done on a supper carrier (USS America) that you can't get any relay information on.

Quoting sprout5199 (Reply 15):As far as torps are concerned, not sure armor can do anything.

The solution with torpedoes for a CVN are double bottoms and size really. There have been all sorts of solutions throughout the years for battleships (Torpedo defense systems came in all sorts of different flavors in the 1920's and 30's) and some of that knowledge is undoubtedly carried over to carrier construction. The main defense though is that it will be very hard to break the back of a 100,000 plus ton ship like you can a 10,000 ton cruiser.

Quoting BigJKU (Reply 26):This is more than a bit looney. Hitting a CVN with an RPG on the side would be the like firing your pellet gun at an elephant.

I see what you are saying, but if an RPG hit, say, the side of the hangar(having never served on a carrier, don't know the layout) and then hit a aircraft, that would start a mass-conflag. Lots of damage for little cost.

I'm not talking about sinking one, just taking it out of the "fight". And with all the talk of reducing the number of CVN's, losing one for even 6 months is a big deal.

Quoting sprout5199 (Reply 28):I see what you are saying, but if an RPG hit, say, the side of the hangar(having never served on a carrier, don't know the layout) and then hit a aircraft, that would start a mass-conflag. Lots of damage for little cost.

I'm not talking about sinking one, just taking it out of the "fight". And with all the talk of reducing the number of CVN's, losing one for even 6 months is a big deal.

Hangers have impressive fire suppression systems if that were to happen. More than that an RPG has a range of less than 300 meters effective and you won't ever get that close. Finally the best way to think of the hanger on a Nimitz is that it basically starts on the inside edge of the deck-edge elevators so it is not exactly flush up against the outer hull of the ship in most places. If you look at some photos of the hanger you can see the void space when the doors are open. That void space is several feet or more, depending on where it was on the ship.

Quoting sprout5199 (Reply 28):I see what you are saying, but if an RPG hit, say, the side of the hangar(having never served on a carrier, don't know the layout) and then hit a aircraft, that would start a mass-conflag. Lots of damage for little cost.

The most common warhead for an RPG is a shaped charge which results in a focused jet of molten copper. The primary purpose of the weapon is to penetrate thick sheets of armour plating, not create a blast or shrapnel effect (although it does have a small blast charge). The molten copper would probably burst through the outer shell but fail against an inner layer. If the molten copper penetrated to an aircraft and hit something vital it might cause some damage but nothing too great or expansive.

The possibility of someone getting close enough to an aircraft carrier (that had fuelled aircraft in the hanger) to fire an RPG is pretty remote though. The RPG-7 self-detonates if it doesn't hit anything after approximately 920m and I can't see the escorts letting someone get anywhere near that range.

Quoting flyingturtle (Thread starter):The book said that all aircraft carriers are not armored due to an international treaty, so they are less resistant to e.g. torpedoes; and that Japan in World War II built battleships that "accidentally" received an aircraft deck, thus building aircraft carriers that were effectively armored.

Quoting flyingturtle (Reply 4):Quoting par13del (Reply 1):
What we know from WWII is that the UK had armoured deck carriers and suffered less damage than the US Navy whose decks were unarmoured.

Thank you, but I knew that difference between British and U.S. carriers.

Quoting sprout5199 (Reply 12):There was two rubber belts that circled the ship 1/3 and 2/3rds the length, to prevent "hogging" and the bridge was like 100 feet above the water line, must have been fun in high seas.

Indeed it would have been. Dumb question, but wouldn't adding armour to the deck increase the roll moment ? Not knowing much about naval design, but carriers to me sit high in the water, so adding armour would raise the CoG significantly. BB's and CGs, OTOH, seem to ride a lot lower in the water, and much of the armour would probably be at or near the waterline.

Quoting connies4ever (Reply 31):Indeed it would have been. Dumb question, but wouldn't adding armour to the deck increase the roll moment ? Not knowing much about naval design, but carriers to me sit high in the water, so adding armour would raise the CoG significantly. BB's and CGs, OTOH, seem to ride a lot lower in the water, and much of the armour would probably be at or near the waterline.

Yes, armor plating at the flight deck level would raise the center of gravity and decrease stability (all things being equal). Perhaps significantly.

Of course the answer to the question of whether this is a problem or not is "it depends". Decreased stability results in a larger roll period...ironically a 'nicer ride' compared to the stiff, snappy roll period experienced by more stable ships. In the WW2-era flight launch/recovery mode a slower roll period may have been advantageous, I really don't know.

Quoting par13del (Reply 1):What we know from WWII is that the UK had armoured deck carriers and suffered less damage than the US Navy whose decks were unarmoured.
The treaties in force prior to WWII were probably all scrapped by the war, I'm inclined to believe if any current carrier US or otherwise is unarmoured its because of cost and weight.
The historians will chime in I'm sure.

As others have said both the USN and RN "armored" their carriers with horizontal (deck) protection. The US did it on the hanger deck. The RN did it on the flight deck.

What I want to focus on here is the idea that British ships were tougher. Most of these conclusions are from kamikaze attacks at the end of the war. It is important to remember that no ships were really designed with this in mind. It was a unique situation that was outside of the realm of design.

The British Carriers did hold up well (operationally if not longevity wise as someone already detailed) to kamikaze strikes but this in and of itself does not validate the design decision to armor the deck. The strikes that hit the decks of the British Carriers were exclusively Zero's carrying nothing more destructive than 500ish pound bombs. The biggest issue I have with armored decks is that they would have been found essentially useless against AP bombs of higher weights that would enter service on more powerful aircraft in 1943 or so. More than that the real killer of ships was likely to be properly delivered aerial torpedoes.

I don't like trading air wing size for flight deck armor much at all. The development of radar made a CAP very valuable and USN carrier damage and losses were really very low once this technology matured until the kamikaze attacks began. It was more of a happy bit of luck that the RN had carriers that were particularly resistant to that means of attack (fairly shallow angle, comparatively low speed compared to a falling AP bomb and light weapons).

Without reading the treaty (and the definitions stated in it), this may be incorrect, but when referring to tonnage of the ship, they may be referring to the gross tonnage, which is a measure of volume of the ship as opposed to physical weight. this sort of measurement would limit ship size, but would not limit hull thickness as it is an internal measurement IIRC (sorry its been a few years since I've taken my courses on naval affairs)

Quoting connies4ever (Reply 31):Indeed it would have been. Dumb question, but wouldn't adding armour to the deck increase the roll moment ? Not knowing much about naval design, but carriers to me sit high in the water, so adding armour would raise the CoG significantly. BB's and CGs, OTOH, seem to ride a lot lower in the water, and much of the armour would probably be at or near the waterline.

BBs had enough armor that a high CG was a problem for those as well. The really heavy guns mounted high on the ship, were a significant contributor as well (and the turrets carried a fair big of armor as well). A number of BBs that were up-gunned or up-armored during their lives grew blisters to compensate for the increases top-side mass (and often doubled as part of enhanced torpedo protection).

Quoting bigjku (Reply 33):The British Carriers did hold up well (operationally if not longevity wise as someone already detailed) to kamikaze strikes but this in and of itself does not validate the design decision to armor the deck. The strikes that hit the decks of the British Carriers were exclusively Zero's carrying nothing more destructive than 500ish pound bombs. The biggest issue I have with armored decks is that they would have been found essentially useless against AP bombs of higher weights that would enter service on more powerful aircraft in 1943 or so. More than that the real killer of ships was likely to be properly delivered aerial torpedoes.

By 1942, the British had realized that the sacrifices they were making for the heavy protection of an internal hangar could not be justified and they went to an external hangar much along the US lines. Okinawa proved this point; although often quoted as pointing to the value of an armored deck, careful analysis does not bear this out.

The British carriers never came under the weight of attack that the US carriers suffered and never took the same density of hits. For example, during the Okinawa campaign, the Americans were operating four times as many fast carriers as the British, and the weight of Kamikaze attacks against them was many times greater again: ten Kikusui (massed suicide attacks) being flung against them whereas there were no such attacks on the British carriers. A tally of Japanese aircraft lost during this time illustrates the disproportionate burden; the American TF 58 (including fifteen fast carriers) destroyed 1,908 Japanese planes, while the British TF 57 with its four fast carriers managed only 75 kills.

Despite this glaring disparity, kamikazes damaged four carriers in each task force - every British carrier suffered at least one hit. The only armored carrier to reach war’s end without kamikaze damage was Implacable, which arrived on station at the end of the Okinawa campaign.

But again, armor was not a solitary factor in limiting the casualties. A critical factor seems to have been deck parks - if the stricken carrier had deck-parked aircraft, she was in trouble regardless of where her hangar was. The British never faced the prospect of a kamikaze hit amid an American-sized crowd of armed and fueled aircraft. The restricted air group had this ironic side-benefit; it provided less kindling in case of fire. Avgas storage, a proven killer of carriers, was severely limited as was aircraft weaponry. In this case, the fact that Illustrious presented a lesser threat to the enemy also made her a tougher target - analogous perhaps to sending a battleship into action with only a few rounds of ammunition in hopes of preventing a magazine explosion.

It is not immediately apparent, but most Kamikaze hits bounced off US carriers doing little or no damage - the ones that started the big fires were the exception.

Quoting bigjku (Reply 33):The British Carriers did hold up well (operationally if not longevity wise as someone already detailed) to kamikaze strikes but this in and of itself does not validate the design decision to armor the deck. The strikes that hit the decks of the British Carriers were exclusively Zero's carrying nothing more destructive than 500ish pound bombs. The biggest issue I have with armored decks is that they would have been found essentially useless against AP bombs of higher weights that would enter service on more powerful aircraft in 1943 or so. More than that the real killer of ships was likely to be properly delivered aerial torpedoes.

True, however in the 1930's when these carriers were designed, they presumably looked at what potential enemies had in terms of aircraft/ordnance, meaning for the most part, Italy.
But the point made previously about the quality of FAA aircraft makes sense too, between 1918 and 1938 the FAA's priority level as effectively part of the RAF - fixated as they were with bombers until the late 1930's too - probably wasn't much higher than what paint to use on RAF airfields.
Not helped by some eccentric ideas on aircraft design within the FAA itself.

Quoting GDB (Reply 37):True, however in the 1930's when these carriers were designed, they presumably looked at what potential enemies had in terms of aircraft/ordnance, meaning for the most part, Italy.

Incorrect.

Wartime exploits in the Mediterranean have given a false impression that the armored carriers were intended specifically for that narrow-seas setting, but Britain had worldwide commitments. The Admiralty’s eyes, roving over the vastness of the Indian Ocean and South China Sea, never myopically fixed on a European land-based air threat. Difficult negotiations with Japan raised the immediate prospect of a Far East war, this threat was linked to to the Admiralty’s prevailing battle doctrine. Fleet projections in the mid-1930’s revealed the true priorities, calling for the deployment of eight fleet carriers - five of them to the East. The narrow European seas, often touted as the reason for the armored box, exerted minimal influence. The Mediterranean hadn’t suddenly shrunk after Ark Royal was designed.

Quoting ThePointblank (Reply 36):By 1942, the British had realized that the sacrifices they were making for the heavy protection of an internal hangar could not be justified and they went to an external hangar much along the US lines. Okinawa proved this point; although often quoted as pointing to the value of an armored deck, careful analysis does not bear this out.

The Japanese had the worst of both worlds. Their carriers had unarmored flight decks and enclosed hangar bays. As was seen at the Battle of Midway once those hangars took hits and fully armed and fueled aircraft started cooking off the ships were ripped apart. Fueling and arming planes along with poor damage control practices did not help either.

Quoting spqr (Reply 34):Without reading the treaty (and the definitions stated in it), this may be incorrect, but when referring to tonnage of the ship, they may be referring to the gross tonnage, which is a measure of volume of the ship as opposed to physical weight. this sort of measurement would limit ship size, but would not limit hull thickness as it is an internal measurement IIRC (sorry its been a few years since I've taken my courses on naval affairs)

From the Treaty:

************

STANDARD DISPLACEMENT
The standard displacement of a ship is the displacement of the ship complete, fully manned, engined, and equipped ready for sea, including all armament and ammunition, equipment, outfit, provisions and fresh water for crew, miscellaneous stores and implements of every description that are intended to be carried in war, but without fuel or reserve feed water on board.

The word "ton" in the present Treaty, except in the expression "metric tons", shall be understood to mean the ton of 2240 pounds (1016 kilos).

Vessels now completed shall retain their present ratings of displacement tonnage in accordance with their national system of measurement. However, a Power expressing displacement in metric tons shall be considered for the application of the present Treaty as owning only the equivalent displacement in tons of 2240 pounds.

A vessel completed hereafter shall be rated at its displacement tonnage when in the standard condition defined herein.

************

So clearly they were worried about displacement (weight), which does make more sense than the old volumetric way of measuring "tonnage" when you are talking about warships.

Quoting Ozair (Reply 30):The possibility of someone getting close enough to an aircraft carrier (that had fuelled aircraft in the hanger) to fire an RPG is pretty remote though. The RPG-7 self-detonates if it doesn't hit anything after approximately 920m and I can't see the escorts letting someone get anywhere near that range.

I have a picture in my mind of some guy (or girl) in the combat data center moving the mouse over the target on his screen, right click, select from: kill, obliterate, vaporize. left click. problem solved.

Quoting aklrno (Reply 41):I have a picture in my mind of some guy (or girl) in the combat data center moving the mouse over the target on his screen, right click, select from: kill, obliterate, vaporize. left click. problem solved.

It was a long time ago - mid-80s - but SLQ-32 EW operators on frigates and destroyers used to say they played the most realistic video game in the world. If they lost, they died.

Quoting LMP737 (Reply 39):The Japanese had the worst of both worlds. Their carriers had unarmored flight decks and enclosed hangar bays. As was seen at the Battle of Midway once those hangars took hits and fully armed and fueled aircraft started cooking off the ships were ripped apart. Fueling and arming planes along with poor damage control practices did not help either.

However, a bomb hit among a large group of aircraft parked on the deck while being armed and fuel is disaster for any aircraft carrier, armored or unarmored, enclosed hangar deck or open.

Quoting rfields5421 (Reply 22):CV-41 - the last USS Midway - laid down Oct 1943 - commissioned 10 Sep 1945 - had some limited armor. By the time I was stationed in Yokosuka in 1982 - I don't think she had any special armor left. During her 1986 dry dock in Yokosuka - the added sea keeping blisters (I don't know if they were in addition or replacement of previous blisters).

Correction: The Midway class is a much more complex design problem than just the adoption of an armored deck. In fact, the armored deck was not actually adopted - it grew out of other factors in the ship's design. Norman Friedman's "US Carriers - An Illustrated Design History" goes into this in detail, but, in summary, the Midway's were the first non-treaty restricted carrier designs in the US Fleet. British input to the design was actually very mixed - even after the Illustrious bombing (usually quoted as an example of the value of an armored deck), some British comment to the US Navy was very anti-deck armor. In the most famous Mediterranean incident, Illustrious survived numerous hits, but only one 500-kg bomb found her deck armor.

Originally, the Midway's were to have had a heavy (8 inch) deck gun battery. Eventually, this was discarded and the weight saved was used to provide two inches of flight deck armor. This was in addition to the 3.5 inches of hangar deck armor sported by the Essex's. The suggestion that they are a response to the UK armored carrier designs is largely a myth - the discussions that lead to the Midway's actually predate the Illustrious class.